iOS 使用十六进制生成颜色

首先，对String 进行一次扩展：

extension  String {

    subscript (r: Range<Int>) -> String {

        get {

            let startIndex = self.index(self.startIndex, offsetBy: r.lowerBound)

            let endIndex = self.index(self.startIndex, offsetBy: r.upperBound)

            return String(self[startIndex..<endIndex])
        }
    }
}

然后对UIcolor 进行扩展

extension  UIColor{

    static func ColorWithHexString(hex:String) -> UIColor {

        /*let redStr = hex[1..<3]

        let greenStr = hex[3..<5]

        let blueStr = hex[5..<7]*/

        // 存储转换后的数值

        var red:UInt32 = 0, green:UInt32 = 0, blue:UInt32 = 0

        // 分别转换进行转换

        Scanner(string: hex[1..<3]).scanHexInt32(&red)

        Scanner(string: hex[3..<5]).scanHexInt32(&green)

        Scanner(string: hex[5..<7]).scanHexInt32(&blue)

        return self.init(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: 1.0)
    }
}